Method of and apparatus for controlling electrical devices



Oct. 24, 1933. R, B. HUNTER 40.

METHOD OF AND APPARATUS FOR CONTROLLING ELECTRICAL DEVICES Filed Dec. 26, 19s1 ,4 Sheets-Sheet 1 ucamdw B w 82 M MXAW Oct. 24, 1933. R. B. HUNTER 1,932,040

METHOD OF AND APPARATUS FOR CONTROLLING ELECTRICAL DEVICES Filed Dec. 26, 1931 4 Shets-Sheet 2 Oct. 24, 1933., R. B. HUNTER 1,932,040

METHOD OF AND APPARATUS FOR CONTROLLING ELECTRICAL DEVICES Filed Dec. 26, 1951 4 Sheets-Sheet '3 R. B. HUNTER 1,932,040

METHOD OF AND APPARATUS FOR CONTROLLING ELECTRICAL DEVICES Oct. 24, 1933.

Filed Dec. 26

w w m x 5 13 v 1 d I "660 m 1 w a .1 H 0 .i ,1] 1- 5 :0 H6100 Au a w E a? 1 j 8 5 0 5 046 0 07. GH flflfl K UH H M Patented Oct. 24, 1933 PATENT OFFICE METHOD OF AND APPARATUS FORK CON- TROLLING ELECTRICAL DEVICES Richard B. Hunter, Shorewood, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application December 26, 1931 Serial No. 583,344

22 Claims. (01. 175-312) This invention relates to improved methods of and apparatus for controlling electrical devices, and more particularly to methods of and apparatus for controlling illumination intensities of groups of electric lamps.

The control system herein disclosed is in certain respects similar to the control systems described and claimed in my co-pending applications, Patents Nos. 1,906,859 and 1,906,860, both dated May 2, 1933; but involves certain obvious structural and operative advantages thereover.

An object of the invention is to provide novel methods of and apparatus for eifecting multiplescene preselection and enactment of the illumination intensities of a plurality of groups of electric lamps.

Another object is to provide simple mechanical means for registering the adjustment of various elements of the control system during production of a given illumination efiect by the groups of lamps jointly, whereby such illumination effect may thereafter be reproduced exactly regardless of the instant positions of the several control elements respectively.

Another object is to provide simple and eillcient means for varying at will the rate of automatic change from any given position of an illumination intensity control element to any other position preselected therefor.

Another object is to provide an extremely flexible system of illumination intensity control for a plurality of groups of electric lamps, and wherein a minimum amount of skill is required for proper manipulation thereof.

Another and more specific object is to provide for preselection of a substantially unlimited number of illumination efiects, including intensity control, of a plurality of groups of electric lamps, and to provide for subsequent enactment of the various illumination effects in any desired sequence at will and in a semi-automatic manner.

Another object is to provide a simple combination of mechanical and electrical elements to provide for definite preselection of the relative rates of change of illumination intensity of the individual groups of electric lamps.

Another object is to provide a combination of the character last-mentioned involving use of a common driving means for the illumination intensity control elementsof a plurality of the lamp circuits. 7

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modificationin certain respects within the scope of the appended claims.

In the drawings, Figure 1 illustrates schematically and diagrammatically an illumination .control system embodying my invention.

Fig. 2 is a similar view of a modified form of illumination control system embodying my invention.

Fig. 3 is a plan view of a form of gag-plate which may be employed in conjunction with other elements of my device,-the latch members on the gag-plate being shown in certain adjusted positions thereof respectively to provide for enactment of a given combination of illumination intensity effects of the respective groups of lamps uponjoint movement of the sending rheostat elements,-all of which are shown in their lower extreme positions.

Fig. 4 is a sectional view substantially on the line 4--4 of Fig. 3, and on the line 4-4 of Fig. 5.

Fig. 5 is a sectional view substantially on the line 5-5 of Fig. 3, and on the line 5-5 of Fig. 4.

Fig. 6 is a fragmentary-side elevation of one of the sending rheostat handles and the adjustable latch or limiting means therefor.

Fig. '7 is a rear elevation of the parts shown in Fig. 6.

Fig. 8 is a view, partly in vertical section and partly in elevation, illustrating one of the individual driving units shown more or less diagrammatically in Fig. 1, and v Fig. 9 is a detail plan view of certain of the associated parts of a pair of speed selector switches shown in Figs. 1 and 2.

Referring first to Fig. 1 of the drawings,-I have illustrated, by way of example, two groups of electric lamps, continuity of circuit andintensity of illumination of the lamps in the respective groups being subject to control by a system constructed in accordance with my invention; it being understood that in practice a considerably larger number of lamp groups will ordinarily be employed,-the control elements being merely duplicated for each additional group of lamps, as will be pointed out more clearly hereinafter. The two groups of lamps are designated in general by the reference characters 15 and 16. It is to be understood, of course, that any desired number of lamps may be embodied in each group.

Included in circuit with each group of lamps 15 and 16 is a, suitable current controlling or regulating device, such as the dimmer rheostats designated respectively by the numerals 1'7 and I 18. As-will be apparent to those skilled in the art similar or equivalent regulating devices may be substituted for the dimmer rheostats illustrated-as, for instance, electron tubes with grid control, or magnetic amplifier type dimmers in which the current in the direct current coils is varied.

Normally open electromagnetically operable switches 19 and 20 are also included in circuit with the respective groups of lamps,--singlepole double-throw selector switches 21 and 22 being provided, each of said switches as shown being adapted in one of its closed positions to directly connect the operating winding of its associated electromagnetically operable switch across lines L and L, and each 0! said switches 21 and 22 being also adapted in the other closed position thereof to relay control of the energizing circuits of the windings-oi switches 19 and 20 to a single-pole single-throw master switch 23. I! it be assumed that the lamps in groups 15 and 16 are of like color, white, for instance, then the switch 23 may be considered a color master switch for simultaneous control of con tinuity of circuit of the groups of lamps of that particular color. Other groups of lamps (not shown) oi different colors may be provided with individual circuit continuity control switches corresponding to the switches 21 and 22 aforementioned, and color master switches corresponding to switch 23 may be provided for simultaneously controlling continuity of circuit of a. number of groups of corresponding color. Moreover, in such an installation the color master switch 23 and corresponding master switches for the other groups of, lamps of different colors would be provided with a second closed position to provide for relaying of circuit continuity control to a single-pole single-throw switch (not shown) which would act as a grand master. An arrangement of circuit continuity control switches of the character just mentioned is disclosed in my aforementioned application, Serial No. 488,185, and further description thereof herein is deemed \mnecessary.

energization and closure of the switches 19 and 20, the circuits of the groups of lamps 15 and 16 will be completed,the intensity of illumination of the lamps in each group being dependent upon the respective positions of the contact arms 17, Iii of the dimmer rheostats. Each of said arms 1'7, 18" is shown in its lower extreme position, which may be assumed to pro vide for full-dark or zero illumination intensity of the respective groups of lamps, it being understood that when the arms 17, 18 are in their respective mid-positions, half-bright illumination intensity of the respective groups of lamps is provided-and when arms 17*", 18 are in their upper extreme positions full-bright illumination intensity of the respective groups of lamps will be provided.

Means are associated with each group of lamps to provide for movement or adjustment of the aforementioned rheostat contact arms 17, 1B automatically Irom any given position or positions thereof to any other preselected position or positions, e position to be assumed by each rheostat contact arm being initially preselected individually (as during rehearsal) to provide the desired illumination effect of certain or all of the groups of lamps jointly,--whereuponthe adjustments so effected are definitely registered upon a suitable gag-plate or the like to provide for subsequent enactment of the exact illumination effeet so preselected for that particular scene. As will be understood the gag-plates are all of like construction, and in practice one gag-plate will be used for enactment of the illumination effect for each particular scene, so that the total number of gag-plates employed will correspond with the total number of scenes or illumination efiects to be enacted.

Thus as shown in Fig. 1 the means for preselecting the position and effecting movement of the contact arm 1'7 of dimmer rheostat 17 comprises essentially a sending rheostat 24 an adjustable contact arm 24* therefor, a receiving rheostat 25, an adjustable arm 25 therefor, and the coil '26 of a polarized relay of known form,- said rheostats 24, 25 and coil 26 being connected with respect to each other and with respect to lines L L in the form of a Wheatstone bridge. The contactor 26 of the polarizer relay is normally biased to an intermediate or neutral position, as illustrated, when the bridge circuit is in balanced condition, and the same is moved auto matically into engagement with the stationary contacts 26, 26, selectively, depending upon the sense in which the bridge circuit becomes unbalanced. The controlling eflfect of the Wheatstone bridge circuit and its associated parts is described in detail in my aforementioned application, Serial No. 488,185.

The means for controlling the intensity of iilumination of the group of lamps 16 similarly comprises a Wheatstone bridge circuit including a sending rheostat 27 and contactor 27*, receiving rheostat 2,8 and contactor 28 and a polarized relay having a coil 29, contactor 29', and stationary contacts 29 and 29. If desired switches 30 and 31 may be provided, the same being adapted when open to disable or de-energize the respective Wheatstone bridge circuits.

The details of construction of my illumination control system and one method of operating the same will now be described. Thus assuming that during rehearsal of a scene it is desired to provide a given lighting eflect. Switches 21 and 22 will be moved into engagement with their respective contacts 21, 22 to eiTect energization and closure of the relays 19 and 20 whereby the groups of lamps 15, 16 are connected across lines L 1.. either exclusive of the respective resistances of dimmer rheostats 17, 18 or inclusive of portions thereof, as determined by the particular positions of the contactors 1'7, 18. Assuming closure of the aforementioned switches 30 and 31 it will be seen that the respective Wheatstone bridge circuits are energized, but no current will flow in either direction through the relay coils 26, 29 due to balancing of the bridge circuits, as evidenced by the relative positions or the rheostat contactors 24 25* and 2'7, 28. The rheostat contactors 1'1, 25 and 18, 28* are shown as mechanically connected with but insulated from each other; and as aforeindicated the illustrated positions of contactors 1'7, 18 will provide for full-dark or zero intensity of illumination of the groups of lamps 15, 16. ,The contactor 2'7 of sending rheostat 27 is likewise shown at the upper left hand side of Fig. 1 to indicate the manner in which the operating handles of the various sending rheostat handles are correlated to Iacilitate operation thereof. The gag-plate 32 is preferably omitted during manual adjustment of the sending rheostat contactors 24, 2'7, etc., to obtain the desired illumination effect for a given scene,--say scene one.

Thus the contactors 24, 27 may be moved by hand to various trial positions within their respective ranges,the follow-up means aforedescribed acting automatically to effect gradual balancing of the bridge circuits, with resultant movements of the dimmer rheostat arms 17*, 18 to positions corresponding to the respective positions of contactors 24 27 The amount of time required toobtain a desired illumination effect during rehearsal will of course depend to some extent upon the number of groups of lamps involved and upon the skill of the operator.

Immediately upon attainment of the desired illumination effect for a given scene, a gag-plate 32 may be applied over the handles 24 27 33 and 34 which are attached to but insulated from the contactors 24, 27 33 and 34 of the respective sending rheostats,contactor 33 being associated with the sending rheostat forming a control element for an additional group of lamps (not shown) and contactor 34 being associated with a master sending rheostat 34 which is adapted to function in the manner hereinafter described.

One form of gag-plate 32 adapted for cooperation with the handles of four sending'rheostat contactors is shown more in detail in Figs. 3 to 7, and as shown the same is provided with a number of slots 32 to provide clearance for the respective sending rheostat contactor handles, and a like number of slots 32 within which the several adjustable latch members 32 are adapted to slide. It will of course be understood that in a given installation a much larger number of groups of lamps may be controlled, and accordingly a gag-plate having an increased number of slots and latch members may be utilized. Where the installation involves control of a relatively large number of (say, fifty or more) groups of lamps it may be desirable to form the gag-plate with a number of parallel rows of slots, for convenience in mounting the various parts of the control system to minimize the space requirements and to facilitate manipulation of the control elements.

Since in practice it is found that only a small proportion of the total number of groups of lamps will be required to be energized and/or controlled for enactment of a given illumination effect, it is preferred to store the gag-plates prior to rehearsal with all of the latch members in their lower extreme positions which correspond to full-dark or zero intensity of illumination of the respective groups of lamps to be controlled thereby. Thus it maybe assumed that when gag-plate 32 (Fig. 3) was placed in position as illustrated all of the latch members 32 were in their lower extreme 'positions,the second latch member from the right hand side of the gag-plate in Fig. 3 being shown in such lower extreme position.

Each of the latch members 32 comprises a handle the diameter of which is greater than the width of its cooperating slot 32 said handle having a reduced and threaded intermediate portion which extends through the slot (as illustrated in dotted lines at 35 in Fig. 6) for cooperative engagement with a tapped opening in clamping plate 36. Plate 36 is provided at opposite ends thereof with openings to receive with a drive fit the pins 37 and 38, the heads 37, 38 of said pins being positioned within the slot to guide and po- J sition the latch member as a whole, and the inner ends of said pins projecting rearwardly beyond said plate to act as stops for the element 39 which is pivotally supported upon the still further reduced inner end portion 40 of the handle; a washer 41 and a cotter pin 42 or the like being employed to retain element 39 in position. Interposed between plate 36 and element 39 is a coiled torsion spring 43 one end of which is hooked about the pin 38 and the other-end of which is bent upwardly to engage an opening 39 to bias element 39 in a clockwise direction to the position thereof shown in Fig. 7.

Each of the handles of the sending rheostat contactors (as for instance the handle 27 is provided with a projection 44 normally positioned in the plane of the element 39 whereby upon upward movement of the latter the angular edge 39 thereof engages projection 44 and is thereby caused to move in a counterclockwise direction (Fig. 7) against the bias of spring 43 to clear said projection. Thereafter the latch member may be moved downwardly to bring the edge or shoulder 39 thereof into engagement with projection 44. Thereupon the handle of the latch member may be turned in a clockwise direction to draw plate 36 into clamping engagement with the gag-plate 32 to positively prevent further upward movement of the rheostat contactor handle.

It is desirable, however, to provide for movement of each of the rheostat contactor handles at will, and accordingly the latter are pivotally supported at 45 by the members 46 which are here shown as being formed of insulating material. Each rheostat contactor handle is biased by means of a tension spring 47 to the normal position thereof shown in full lines in Figs. 6 and I, and the same is tiltable manually (as shown in dotted lines in Fig. 6) to throw the projection 44 out of the plane of latch element 39, whereby unobstructed upward movement of the handle is permitted. A projection 48 formed on each handle engages a suitably shaped edge 49 upon the respective member 46 (shown in dotted lines for clarity of illustration in Fig. 6) whereby the pivotal movement of the handle in each direction is properly limited.

I have provided novel means for effecting movement of the rheostat contactors either individually or jointly at will in either direction, the degree of movement of the several contactors when moved jointly in one direction being of course dependent upon the setting of the individual latch members when the gag-plate is employed. Thus each of the four rheostats illustrated (see Fig. 5) comprises a base 50 formed of a suitable heat-resisting and electrical insulating material, and each base has wound thereabout the desired number of turns of resistance wire 24, 27, 33 and 34, said turns being spaced a predetermined distance from each other, as best illustrated in Fig. 4. A coating 50 of insulating cement is preferably applied to retain the turns of the resistance wire in properly spaced relation, portions of the respective turns of the wire being left exposed at the outer arcuate edge of the base 50 to provide for engagement therewith of the rheostat contactors 24 27 33 and 34 The bases 50 are preferably supported in pairs in an end to end relation, one pair being shown attached to and spaced from a pair of bracket 1 0 members 51 and 52, as by means of screws 51. 52 and ferrules 51 The other pair of bases 50 is attached in a like manner to a pair of brackets one of which is shown at 53. Said pairs of brackets are respectively attached to a pair of insulating base members 54 and 54 (Figs. 4 and 5), and said base members are attached in a suitable manner to a box-like metal frame, designated in general by the numeral 55.

Frame 55 includes a top plate 56 which is slotted as shown to accommodate the members 46 aforementioned. The upper member 46 illustrated in Fig. 5 is rigidly secured to a metal plate 57, which may be of rectangular form if desired, and attached to the opposite end of plate 57 is a metal member 46, said member i6 having a notch or slot 46 (Fig. 4) at its outer end to provide an open bearing for the reduced portion of a rod or pin 24 which forms the contactor of this particular rheostat. Pin 24 is provided with a reduced and shouldered end 58 which is adapted to bear within a suitable opening in the metal plate 59 secured in a spaced relation to member 46 as by means of suitable rivets 60. A conductor 61 is attached at one end to the metal plate 57 and at its other end to one of the terminals 62 upon base 54. The opposite ends of resistance wire 24 are likewise connected by suitable conductors 63 and 64 to corresponding terminals 62 upon base 54. A tension spring 59 is interposed between one of the rivets and an intermediate portion of contactor 2i to bias the latter into engagement with the turns of the resistance wire 24.

The contactor 27 associated with resistance element 27 is supported in a manner similar to the contactor 24. The reduced end of contactor 27, however, is adapted to bear within an opening in insulating member 46, and a metal plate 65 is provided with a notch to provide an open bearing for the intermediate reduced portion of said contactor,tension spring 65 acting to bias the contactor into engagement with the turns of the resistance element 27. A bus member 67 provides an electrical connection between contactor 27 and the metal plate 68,the latter having attached thereto a conductor 69 which leads to one of the aforementioned terminals 62 on base 54.

Contactor 33 is supported and actuated in identically the same manner as contractor 24 the metal member 46 of the former being mechanically and electrically connected to metal plate 70, which is in turn connected by conductor 71 with one of the wiring terminals (not shown) on base 54. Contactor 34 is supported and actuated in identically the same manner as contactor 27,-the same being electrically connected with plate 72 as by means of bus member 73, and the latter being provided with a terminal conductor 74.

The common operating means for the several rheostat contactors 24, 27 33 and 34 is shown as comprising a square shaft 75 which extends through opposite sides of the metal frame 55. Said sides of the frame are provided with circular recesses or countersinks 76, 77 in the respective outer surfaces thereof to provide bearings for the washers 76 77 which have square openings to fit upon the opposite ends of the shaft. A cotter pin 76 or the like is attached to the shaft 75 at one end and a handle 77 is attached to the other end of the shaft, as by means of a pin 77. Shaft 75 is thus held against endwise movement with respect to the frame 55.

Rigidly secured in fixed positionwith respect to frame 55, as by attaching the same to brackets 51, 52, 53, etc; are pairs of insulating plates 78, 79 and 80, 81, said plates (as shown at 80, 81 in the lower portion of Fig. 5) having relatively large openings to provide clearance for' the shaft 75 and the respective insulating ferrules or coverings 75 carried by the latter.

Metal members and 72 are provided with relatively large circular openings to accommodate the metal washers 70, 72 which are interlocked for rotation with shaft 75, but insulated therefrom by said ferrule Arranged on opposite sides of members 70, 72 and their washers 70 72 are pairs of insulating washers or members 70* 70 and 72, 72, each of said insulating washers being interlocked with shaft 75 for rotation thereby. Interposed between washers 70 and 72 is a coiled compression spring 82 which acts to hold the pairs of washers 70 ,70 and 72 72 in frictional driving engagement with the respective members 70 and 72. In this manner a slip-clutch driving connection is provided between shaft 75 and each of the members 70, 72, so that the latter are normally movable jointly in either direction along with said shaft. Also as will be apparent the members 70 and 72 are movable in either direction independently of each other and independently of shaft 75, as by means of the respective handles 33 34 In like manner slip-clutch driving connections are provided between shaft 75 and the members 57 and 68.

The operation of the parts heretofore described will now be readily understood. Thus in the absence of gag-plate 32 all of the members 57, 68, 70 and 72 and their associated parts may be moved jointly to their respective extreme positions by merely rotating the shaft 75 in one direction or the other, as by means of handle 77 Also as aforestated, each .of the members 57, 68, 70 and 72 may be moved, independently of all the others, to any angular position within its range, whereby any desired adjustment of the individual rheostat contactors 24, 27, 33 and 34 may be effected.

Let it be assumed that the illumination effect for scene one has been enacted and that it is desired to change to the illumination effect preselected for scene two. In this case the gag-plate which was utilized for effecting enactment of the illumination effect for scene one is removed and a gag-plate having the latch members properly adjusted to provide the illumination effect for scene two is placed in position. Thereupon the shaft 75 is quickly moved in a counterclockwise direction (Fig. 4) to return all of the rheostat contactors to the positions thereof which would eventually provide for full-dark illumination intensity of their respective groups of lamps. Said contactors may be allowed to remain in the extreme positions thereof last mentioned to provide for gradual dimming of the previously active groups of lamps. In most instances, however, it will be preferred to initiate enactment of the illumination effect preselected for scene two prior to gradual extinguishment of the groups of lamps which were active for scene one. Accordingly after the aforementioned counterclockwise movement of shaft 75 the same may immediately be moved in a clockwise direction through the required range (which range will preferably be fixed, as by suitable stops. to cover. the complete range of arcuate niovement of the respective rheostat contactors), whereby joint movement of the rheostat contactors to the respective positions preselected therefor is effected. The follow-up control means individual to each group of lamps then acts automatically in the manner aforedescribed to enact the illumination effect preselected for scene two.

As will be understood by those skilled in thecuits of the several polarized relay contactors) to insure against any change in the intensity of illumination of the respective groups of lamps during movement of the several contactors of the sending rheostats from the positions thereof preselected for one scene to the positions thereof preselected for the next succeeding scene; In this manner the necessity for rapid movement of the sending rheostat contactors is eliminated.

Referring again to Fig. 1, wherein I have shown an individual driving motor for each of the dimmer rheostat contactors 17 and 18, said motors having split-field windings 83 83 which are adapted when energized selectively to provide for forward or reverse operation thereof. Each drive includes a slip-clutch connection 84, a driven shaft 85 having a gear 86 fixed thereto, a pivoted latch 87 biased into locking engagement with said gear, as by means of a spring 83, a solenoid 89 adapted when energized to retract said latch, and suitable gearing 90 to transmit the motion of shaft 85 to contactor 17.

A relay 91 having two sets of normally open contacts 91 and 91 is provided with a winding 91, the energizing circuit of which is completed upon closure of the polarized relay contacts 26, 26. Contacts 91 when closed are adapted to complete a circuit for motor 83 through the field winding 83 whereby operation of the motor in one direction is effected, and contacts 91 when closed are adapted to preset an energizing circuit for the solenoid winding 89, completion of which circuit is subject to control by a speed-selector switch 92. the function of which will be hereinafter described in detail. I

A second relay 93 having two sets of normally open contacts 93 and 93 is provided with a winding 93, the energizing circuit of which is completed upon closure of the polarized relay contacts 26, 26. Contacts 93 when closed are adapted to complete an alternative circuit for motor 83, through the field winding 83 whereby operation of the motor in the reverse direction is effected, and contacts 93 wh'en closed are adapted to preset an alternative energizing circuit for the solenoid winding 89, completion of which circuit is likewise subject to control by the speed-selector switch 92.

In order to clearly explain the purpose of the speed selector mechanism it may be assumed that the speed of motor 83 and the ratio of gearing is such that with the latch member 8'7 retr'acted .the dimmer rheostat contactor 17 (or 18) could be moved automatically in either direction throughout its entire range within a period of two seconds, to provide for a change from full-dark to full-bright or full-bright to full-dark intensity of illumination of the group of lamps controlled thereby within said period of time. On the other hand, it is desirable at times to provide for variation of the rate of change from one intensity of illumination to another, and the particular means herein disclosed provides for selection of various different speeds of travel of the dimmer rheostat contactor 17* (or 18 varying from full range movement in two seconds, as aforedescribed, to full range movement in fifteen minutes. to provide for selection of different rates of speed for the dimmer rheostat contactors individually and the means herein described is particularly adapted for accomplishment of this result.

Thus I have shown a synchronous motor 94 which may be assumed to have a speed of 1800 R. P. M. A drum 95 is driven by motor 94 through Moreover, it is extremely advantageous gearing 96 which provides for operation of said' drum at a speed of 600 R. P. M. Drum 95 is provided with pairs of segments 9'7, 98 and 99, 100

which are preferably arranged in the manner illustrated,-the segments 9'7, 98 of equal length being vertically alined to provide for completionv and interruption of a circuit at the contact fingers 101, 102 under given conditions, and segments 99, 100 being arranged to cooperate with contact fingers 101, 103 in a like manner. Contact fingers 101, 102 and 103 are adjustable to different angular positions with respect to the periphery of the drum whereby arcing between segments 97 to 100 and their cooperating contact fingers 101, 102 and 103 may be minimized. It is to be understood that the length of segments 97, 98 will be so chosen with respect to the perimetric dimension of drum 95 and the speed of operation thereof as to provide an electrical impulse of given duration incident to engagement of said segmentswith their respective contact fingers,while, as aforeindicated, insuring make and/or breakof the circuit when the alternating current is of substantially zero value. The length of segments 99, 100 is such as to provide an electrical impulse of relatively shorter duration, and the position thereof upon the periphery of the drum is such as to likewise insure engagement and disengagement thereof with respect to fingers 101, 103 when the current is of substantially zero value. The arrangement just described. in conjunction with the relatively high speed of rotation of drum 95 effectually minimizes arcing between the drum contacts. I

A second drum 104 is driven by motor 94 110 through gearing which provides for rotation of the former at a speed of 100 R. P. M. Drum 104 is provided with a continuous segment 105 which is connected through contact finger 106 with contact finger 103 of drum 95. Also associated with 5 drum 104 are contact fingers 107 to 111; inclusive; a series of five relatively short segments 10'? being provided to effect five hundred makes and breaks per minute at contact finger 107; a series of four segments .108 being provided to effect four hundred makes and breaks per minute at contact finger 108; and, similarly, three segments 109 for cooperation with contact finger 109; two segments 110 for cooperation with contact finger 110, and one segment 111 for cooperation with contact finger 111,-it being noted that all of the relatively short segments on drum 104 are electrically connected with the continuous segment 105. As will be noted, the segment 100 on drum 95 controls the feed of current to the segments on drum 1.04, and the relative length of said segments and the relative speeds of said drums are so co-ordinated that segment 100 cm gages contact finger 103 just prior to engagement of each of the relatively short segments on drum' 104 with its cooperating contact finger 107 to 111, respectively; and in like manner segment 100 disengages contact finger 103 just prior to disengagement of the segments on druml04 from their respective contact fingers. In this manner all 140 arcing between the segments and contact fingers of drum 104 is eliminated.

Associated with drums 95 and 104 is the aforementioned selector switch 92 having contacts 10l 102 103 107', 108*, 109', 1'10 and 111*, which are electrically connected as shown with the contact fingers 101, 102, 103 and 107 to 11.1, inclusive, of the respective drums,a contactor 92 being movable selectively into engagement with any one of said contacts. As ai'orestated, 150

contactor 92 is included in the circuit of solenoid winding 89, as preset by either of the sets of contacts 91 93 of relays 91 or 93.

More particularly, assuming such positioning of contactor 24 of sending rheostat 24 with respect to contactor 25 of receiving rheostat 25 as to cause unbalancing of the Wheatstone bridge circuit in a sense or direction which will effect engagement of polarized relay contacts 26 and 26 ,an energizing circuit is completed for the winding 91 of relay 91, and contacts 91 are closed to complete a circuit through field 83 of motor 83 to provide for operation thereof in a given direction; contacts 91 of relay 91 being simultaneously closed to preset an energizing circuit for solenoid winding 89 for completion under control of speed selector switch 92 and drums 95 and 104. For instance, if the contactor 92 is engaged with contact 101 under the conditions last mentioned winding 89 will be continuously energized until the Wheatstone bridge circuit is again brought to balanced condition,the circuit of winding 89 extending from line L to contact" finger 101 of drum 95, to contact 101 of selector switch 92, through contactor 92 of the latter and through contacts 91 of relay 91, and thence through said winding 89 to line L Latch 87 will thus be withdrawn from engagement with gear 86 to permit full-speed driving of the mechanically connected rheostat arms 25", 17 by motor 83 through slip clutch 84.

If contactor 92 of selector 92 is engaged with contact 102' the circuit for winding 89 will be alternately completed and interrupted for predetermined proportional periods whereby the latch 87 is alternately engaged with and dis engaged from gear 86 to reduce the speed of operation of rheostat contact arms 25 and 17 by motor 83. The last mentioned circuit for winding 89 extends from line L to contact finger 101 of drum 95, through segments 97 and 98 to contact finger 102, contact 102? and contactor 92 of selector 92, and thence through contacts 91 and winding 89 to line L..

If contactor 92*? is engaged with contact 103*, the circuit of winding 89 is likewise alternately completed and interrupted, but the periods of circuit completion through segments 99 and 100 are relatively shorter than those provided by segments 97 and 98, and hence the speed of operation of'rheostat arms 25 and 17 is further reduced. As aforestated the groups of segments 97, 98 and 99, 100 respectively provide for making and breaking the energizing circuit of winding 89 six hundred times per minute, but the make periods provided by segments 99, 100 are relatively shorter than those provided by segments 97, 98.

Moreover, upon engagement of contactor 92 with contact 10'?' the segments 107 of drum 104 are rendered effective, in conjunction with segments 99', 100 to provide five hundred makes and breaks per minute of the circuit of winding 89,- the "make periods being determined, in the manner aforedescribed by the length of the segments 99, 100. By engaging contactor 92 with contacts 108', 109", 110 and 111, the number of makes and breaks per minute of the circuit of winding 89 may be reduced to four hundred, three hundred, two hundred and one hundred, respectively. ,It can thus be seen that I have provided simple and eificient means enabling preselection of any one of a large number of speeds for the rheostat contactors 25, 17 Also as will be apparent the individual selector switches 92 may be utilized to provide the same or different rate-S 9! GhB-nge in the intensities of illumination of the respective groups of lamps.

Moreover, it is to be noted that with the arrangement aforedescribed definite synchronism in the rates of movement of the rheostat contactors 17 18 etc. is insured, assuming like positioning of the contactors 92 of the selector switches 92. In like manner, if the respective contactors 92 of the switches 92 are positioned differently with respect to each other,' the resulting rates of change in the intensities of illumination of the several groups of lamps will be definitely proportional. This positive control and/0r synchronization of the illumination intensity varying elements is of considerable importance from a commercial viewpoint, since I am thereby enabled to definitely preselect and control not only the illumination effect to be finally obtained, but also the transient or intermediate illumination intensity effects incident to transition from one scene to another.

In practice the contactors 92*- of the selector switches 92 are adjusted as desired for each separate scene during rehearsal, and if desired the adjus'ments of the respective contactors may be registered upon a gag-plate of the character aforedescribed; the contactors 92 being provided with siutable means (not shown) similar to that provided for the sending rheostat contactors 24, 27, etc. to enable joint movement of said contactors 92 as by means of a master control shaft which may be mechanically connected with the master shaft aforementioned to provide for movement jointly with the latter as by means of hand e 77*.

" In Fig. 8 I have illustrated a mechanical arrangement of the driving connections between one of the individual motors 83 and its associa ed rheostat contactors,which parts are shown more or less diagrammatically in Fig. 1. Thus the motor 83 is carried in a vertical position upon a suitable support 112,-the armature shaft 83" of said motor being connected through a flexible coupling with a shaft 113. Said coupling comprises essentially a hollow tubu ar member 114 having alined notches at opposite ends thereof to accommodate the plates 115 and 116 which are attached to and project laterally from the shafts 83* and 113. Keyed to shaft 113, as by means of the transversely extending pin 117 is a pinion 118 which meshes with a gear 119, the latter being keyed or otherwise secured to a hollow shaft 120 for rotation with the latter.

The upper end portion of shaft 120 is cupshaped, as indicated at 121, to accommodate a disk 122 which is riveted or otherwise rigidly secured to a shaft portion 123 for rotation of the latter with the former. Portion, 123 has a driving connection 124 with the shaft 85,-the ar- .thereto a pinion 129 which meshes wi h a gear 86, which is in turn secured to shaft 85. -Gear 86 is provided with a suitable number of depending lugs or projections 86', with any one of which the spring-pressed latch member 87 is adapted to engage when relay coil 89 is de-energized. When latch 87 is so engaged with one of the lugs 86, as indicated in Fig. 8, the disk 122 is of course held stationary and disks 125, 126 are permitted to slip or move with respect thereto. With coil 89 energized, however, latch 87 is retracted to permit-rotafion of gear 86 and shaft 85- attachedv thereto. A flexible coupling is likewise provided between shaft 85 and shaft 85, said connection comprising a hollow tubular member 114 and plates 115, 116 Secured to shaft 85 is a bevel gear 130 which meshes with bevel gear 130, the latter being geared to a s'ub shaft 90 which has a pinion 90 attached to its opposite end. Pinion 90 meshes with gear 90, which latter has attached thereto the shaft 90 Shaft 90 may be directly connected to the rheostat contactors 17 or 28, 18 to effect rotation or oscillation of the latter.

The driving elements just described are preferably attached to a bracket 131 which is in turn attached to a suitable panel or support 132. The

several parts below the driving'connections 114, 114 are carried by a plate or casing 133 which is clamped to bracket 131 by any suitable means (not shown), a body 134 of cork or other resilient and sound-deadening or shock-absorbing ma terial being preferably interposed between said parts. A bracket or yoke 135 is in turn secured to plate 133 by suitable means (not shown), said yoke serving as a support for relay 89 and its associated latch member 87. A receptacle 150 may likewise be attached to bracket 131, said receptacle acting as an enclosurefor the several parts of the drive, and as additional means to reduce the sound of operation thereof.

In Fig. 9 I have illustrated one manner of constructing and supporting the stationary contact elements of a pair of the speed-selector switches 92. As shown, I preferably provide a pair of flat, molded insulating-base members 136, 137

of the desired thickness, said members being respectively provided with straight edges to be arranged adjacent to each other, and outer arcuate edges 136, 137.

, 136, 137 are wound about the respective base members with the coils thereof in definitely spaced relation to each other. With the stripsso wound the same are rigidly secured to the base members, as by applying a coating of vitreous enamel or other suitable insulating cement to certain portions of opposite sides of the respective base members, as indicated at 136 137 Thereafter each coil of the strip-is severed and bent rearwardly to form lugs 136, 137, said lugs being connected by cross-wiring indicated in general by the numeral 138. -Base members 136, 137 are provided with perforations 136 137 whereby the same may be attached by bolts or the like to a suitable support. The contactors of selector switches 92 may be of the character illustrated in Figs. 4 and 5, and said contactors may be arranged in groups to provide for operation thereof independently of each' other or jointly as by means of a master control lever and slip-clutch elements of the character aforedescribed. In like manner suitable gag-plates may be employed to record and reproduce given settings of the several selector switch contactors.

The control system illustrated in Fig. 2 isin most respects identical with that shown in Fig. 1 and the former is adapted to perform the same functions as the latter. In the arrangement illustrated in Fig. 2, however, a single driving motor 83 is provided, said motor being con- Continuous conducting stripsv nected through worm and pinion gearing 139 with a shaft 140 for continuously driving the latter unidirectionally. Shaft 140 has attached thereto a pair of gears 141 and 142. Gear 141 meshes with a gear 143 which is keyed through the medium of shaft 143 with a bevel gear 143 for rotation of the latter. Arranged on opposite sides of' gear 143 is a pair of bevel gears 143 and 143 which are slidably keyed to a shaft 143. Gears 143, 143 are provided with collars or flanges to be engaged by the pivoted yoke members 143 and 143,the latter being normally biased outwardly from each other as by means of'tension springs 143 and 143 whereby gears 143, 143 are disengaged from gear 143*.

Gear 143 is adapted to be engaged with gear 143 upon energization of a coil 144,energization of the latter being subject to control by the contacts 26, 26 of polarized relay 26. With gears 143, 143 thus engaged shaft 143 is rotated in one direction, and through bevel gearing 145 and friction clutch 84 tends to effect movement of rheostat' contactor elements 25?, 1''! in a corresponding direction. Closure of contacts 26, 26 simultaneously effects energization of the operating coil of a relay 146, the contacts 146 of which are closed to preset the energiz-.

Gear 142 likewise meshes with a gear 143 having the associated shaft 143 and bevel gear 143*, the aforedescribed elements 143, 143 143, 143*,

143, 143 143 and 144, 147 being provided for effecting rotation of gearing 145 in reverse directions selectively under control of the contacts 29 29 and 29 of polarized, relay 29,a relay 146 having contacts 146 for presetting the energizing circuit of relay 89 subject to control by the contactor 92 of selector switch 92 being likewise provided.

If desired switches 148 and 149 may be provided for connecting or disconnecting from circuit the respective groups of lamps and the control elements individually associated therewith. The construction and mode of operation of the other control elements of the device shown in Fig. 2 will be apparent from the description of the corresponding elements of the device shown in Fig. 1.

What I claim as new and desire to secure by Letters Patent is:

1. In a control system, in combination, a plurality of resistance elements, a corresponding number of movable contactors adapted for cooperative engagement with the respective resistance elements, common driving means for said contactors, said means comprising an element movable in opposite directions selectively, and a frictional driving connection between-said element and each of said contactors, said frictional driving connection also providing for operation of said contactors independently of each other and of said element.

2. In a control system for electrical devices, in combination, aplurality of resistance elements, a corresponding number of movable contactors adapted for cooperative engagement with the respective resistance elements, common driving means for said contactors, said means comprising a rotatable shaft, and a slip-clutch driving connection between each of said contactors and said shaft, said slip-clutch driving connections also providing for operation of said contactors independently of each other.

3. In an illumination control system, in combination, a plurality of resistance elements, a corresponding number of movable contactors adapted for cooperative engagement with the respective resistance elements, each contactor having an operating handle individual thereto, means for efiecting movement of said contactors jointly,

' said means comprising a rotatable shaft and a slip-clutch connection between each of said contactors and said shaft, said slip-clutch connections also providing for movement of said contactors individually and independently of each other by means of their respective operating handles, means comprising a gag-plate having slots to provide clearance for the respective operating handles, and latch members associated with said slots and cooperable with the respective handles to limit the degrees of movement of the latter upon rotation of said shaft in a given direction.

4. In a control system for electrical devices, in combination, a plurality of resistance elements, a corresponding number of movable contactors adapted for cooperative engagement with the respective resistance elements, each contactor having an operating handle individual thereto, means for effecting movement of said contactors jointly, said means comprising a rotatable shaft and a frictional driving connection between each of said contactors and said shaft, said frictional driving connections also providing for movement of said contactors individually and independently of each other by means of their respective operating handles, means comprising a gag-plate having slots to provide clearance for the respective operating handles, and latch members associated with said slots and cooperable with the respective handles to limit the degrees of movement of the latter upon rotation of said shaft in a given direction, said latch members being pre-adjustable to afford a preselected composite setting of said contactors upon a predetermined degree of unidirectional rotation of said shaft.

5. In an illumination control system, in combination, a plurality of groups of electric lamps, individual intensity control means for the respective groups of lamps, each of said control means including a lever adjustable to preselect the intensity of illumination of its respective group of lamps, common operating means including a friction-drive tending to eflfect movement of said levers jointly toward one extreme position, and adjustable means located in the path of each of said levers to individually limit the degrees of movement of the latter toward said one extreme position by said common operating means.

6. In an illumination control system, in combination, a plurality of groups of electric lamps, individual intensity control means for the respective groups of lamps, each of said control means including a lever adjustable to preselect the intensity of illumination of its respective group of lamps, common operating means including a friction-drive tending to effect movement of said levers jointly toward one extreme position, and adjustable means located in the path of each of said levers to individually limit the degrees of movement of the latter toward said one extreme position by said common operating means, said adjustable means comprising a gagplate having slots to provide clearance for the respective levers, and individually adjustable and pre-adjusted latch means located within each of said slots to be engaged by said levers.

7. In an illumination control system, in combination, a group of electric lamps, means operable automatically throughout a predetermined range'for varying the intensity of illumination of said group of lamps, said means comprising a driving element and a control element with a frictional driving connection therebetween, and means for rendering said driving connection effective or ineffective, said means comprising an electro-magnetically controlled latch, a selector switch and a drum associated with said selector switch, said drum operatively controlling said latch to render said driving connection continuously eilective or intermittently eifective for predetermined periods, to thereby predetermine the rate of movement of said control element.

8. In an illumination control system, in combination, a group of electric lamps, means operable automatically throughout a predetermined range for varying the intensity of illumination of said group of lamps. said means comprising a driving element and a control element with a frictional driving connection therebetween, means for rendering said driving connection eiiective or ineffective, said means comprising an electromagnetically controlled latch. a selector switch and a drum associated with said selector switch, said drum operatively controlling said latch to render said driving connection continuously effective or, intermittently effective for predetermined periods, to thereby predetermine the rate of movement of said control element, and means including a synchronous motor for effecting continuous rotation of said drum, said drum having all of the stationary and movable contacts thereof arranged to minimize arcing therebetween.

9. In an illumination control system including an element operable in reverse directions throughout a given rangeto vary the intensity of illumination of a group of electric lamps, the combination with a motor-operated drive, of a slip-clutch connection between said drive and said element, at latch member spring biased into engagement with a part of said element to render said slip-clutch connection ineffective, an electromagnetic relay adapted when energized to retract said latch whereby said slip-clutch connec tion is rendered eilective, and means including a selector switch operable at will to provide for energization of said relay either continuously or intermittently for predetermined periods, whereby the rate of operation of said element may be definitely preselected.

10. In an illumination control system, in combination, a group of electric-lamps, current control means operable automatically to gradually vary the intensity of illumination of said group of lamps for enactment of a given scene, said current control means being also operable automatically for gradually changing from the obtaining intensity of illumination of said group of lamps to the intensity of illumination thereof preselected for another scene, and means associated with said current control means to control the rate of operation of the latter in each instance, said last mentioned means including a power operated drum and a selector switch operable at will to preselect any one of a number of definite group of lamps regardless of the total change to' rates of change of illumination intensity of said be effected.

11. In an illumination control system, in combination, a plurality of groups of electric lamps, individual current control means operable automatically to gradually vary the intensity or intensities of illumination of the respective groups of lamps for enactment of a given scene, said current control means being also operable automatically for gradually changing from the obtaining intensity or intensities of said groups of lamps to the intensity or intensities of illumination thereof preselected for another scene, and means individually associated with each of said current control means to control the respective rates of operation of the latter in each instance, each of said last mentioned means including means operable at will to preselect any one of a number of definite rates of change of illumination intensity for the group of lamps respectively associated therewith irrespective of the total change to be eifected in such group.

12. In an illumination control system, in combination, a plurality of lamp circuits, individual intensity control elements therefor, individual current regulating means for said lamp circuits to be preset for delayed action subject to control by said intensity control elements respectively, each of said current regulating means including a sending rheostat and a receiving rheostat arranged in the form of a Wheatstone bridge, means controlled by said Wheatstone bridges whereby the respective current changes are effected gradually, and common mechanical means including adjustable parts associated with the individual current regulating means for jointly effecting presetting of the latter for like or different intensities of the several lamp circuits as preselected by the adjustment of said parts respectively.

13. In an illumination control system, in combination, a plurality of groups of electric lamps, individual intensity control elements therefor, individual current regulating means for said groups of lamps to be presetfor delayed action subject to control by said intensity control elements respectively, each of said current regulating means including a sending rheostat and a receiving rheostat arranged in the form of a Wheatstone bridge, means controlled by said Wheatstone bridges whereby the respective current changes are effected gradually, associated means whereby the rates of said current changes may be preselected individually at will regardless of the total changes to be effected, and common mechanical means including adjustable parts associated with the individual current regulating means for j ointly effecting presetting of the latter for like or different intensities of the several lamp circuits as preselected by the adjustment of 'said parts respectively.

14. In an illumination control system, in combination, a plurality of lamp circuits, individual intensity control elements therefor, individual current regulating means for said lamp circuits to be preset for delayed action subject to control by saidintensity control elements respectively, each of said current regulating means including a sending rheostat and a receiving rheostat arranged in the form'of a Wheatstone bridge, means controlled by-said Wheatstone bridges whereby the respective current changes are effected gradually, common mechanical means including adjustable parts associated with the individual current regulating means for jointly. effecting presetting of the latter for like or different intensities of the several lamp circuits as preselected by the adjustment of said parts respectively, said last mentioned means also including a plurality of individually operable control levers, a master control shaft, and slip-clutch driving connections between said master control shaft and each of said individually operable control levers.

15. In an illumination control system, in combination, a plurality of lamp circuits, individual intensity control elements therefor, individual current regulating means for said lamp circuits to be preset for delayed action subject to control by said intensity control elements respectively, each of said current regulating means including a sending rheostat and a receiving rheostat arranged in the form of a Wheatstone bridge, means controlled by said Wheatstone bridges whereby the respective current changes are effected gradually, common mechanical means including adjustable parts associated with the individual current regulating means for jointly effecting presetting of the latter for like or different intensities of the several lamp circuits as preselected by the adjustment of said parts respectively, said last mentioned means also including a plurality of individually operable control levers, a master control shaft, and slip-clutch driving connections between said master control shaft and each of said individually operable control levers whereby the latter are constrained to move jointly with the former between opposite extreme positions, said adjustable parts being respectively adapted to limit the degree of movement of each of said last mentioned control levers.

16. In an illumination control system, in combination, a plurality of lamp circuits, individual intensity control elements therefor, individual current regulating means for said lamp circuits to be preset for delayed action subject to control by said intensity control elements respectively, each of said current regulating means including a sending rheostat and a receiving rheostat arranged in the form of a Wheatstone bridge, means controlled by said Wheatstone bridges whereby the respective current changes are effected gradually, common mechanical means including adjustable parts associated with the individual current regulating means for jointly effecting presetting of the latter for like or different. intensities of the several lamp circuits as preselected by the adjustment of said parts respectively, said last mentioned means also including a plurality of individually operable control levers, a master control shaft, and frictional driving connections between said master control shaft and each of said individually operable control levers whereby the latter are constrained to 135 move jointly with the former between opposite extreme positions, said adjustableparts being 'tion thereof, each of said intensity regulating means comprising a Wheatstone bridge circuit having a part thereof operable at will to preselect a given intensity of illumination of the group of lamps controlled thereby, associated means operable automatically for gradually changing from the obtaining intensity of illumination of such group to the intensity of illumination preselected therefor, and common mechanical means including adjustable parts for effecting movement of said individual parts jointly from any given position or positions thereof to any other position or positions preselected therefor by the adjustment of said parts.

, 18. The method of controlling the illumination intensity or intensities of the electric lamps in a plurality of groups of lamp circuits, each lamp circuit having an intensity control element normally movable at will from a given extreme position thereof to the opposite extreme position thereof, which comprises initially adjusting said intensity control elements individually to provide a given illumination effect by all or certain of said groups of lamps jointly, registering upon a removable member the adjustment of the respective intensity control elements required to provide such illumination effect, effecting a given extreme positioning of all of said intensity control elements, thereafter biasing said intensity control elements for joint movement thereof from the last mentioned extreme position thereof to the other extreme position thereof respectively, and utilizing the adjustment registrations upon said removable member to positively limit the degrees of movement of the respective control elements under such bias.

19. The method of controlling the illumination intensity or intensities of the electric lamps in a plurality of groups of lamp circuits having individual intensity control elements and individual current regulating means to be preset for delayed action subject to control by said intensity control elements respectively, said intensity control elements having parts thereof normally operable individually from given extreme positions to the opposite extreme positions thereof respectively, which comprises initially adjusting said intensity control elements individually to provide a given illumination effect by all or certain of said groups of lamps jointly, registering upon a removable member the adjustment of the respective intensity control elements required to provide such illumination effect, effecting a given extreme positioning of all of said intensity control elements respectively, thereafter biasing said intensity control elements for joint movement thereof from the last mentioned extreme position thereof to the opposite extreme position thereof aforementioned, and utilizing the adjustment registrations upon said removable member to positively limit the degrees of movement of the respective control elements under such bias.

20. The method of controlling the illumination intensity or intensities of the electric lamps in a plurality of groups of lamp circuits having individual intensity control elements and individual current regulating means to be preset for delayed action subject to control by said intensity control elements respectively, said intensity control elements being normally movable at will from a given extreme position to the opposite extreme position thereof respectively, which comprises initially adjusting said intensity control elements individually to provide a given illumination effeet by all or certain of said groups of lamps jointly, registering upon a removable member the adjustment of the respective intensity control elements required to provide such illumination effect, effecting a given extreme positioning of all of said intensity control elements, thereafter biasing saidintensity control elements for joint movement thereof from the last mentioned extreme position thereof to the opposite extreme position thereof aforementioned, utilizing the adjustment registrations upon said removable member to positively limit the degrees of movement of the respective control elements under such bias, and individually preselecting the rates of operation of the respective current regulating means to provide for different predetermined rates of change of the intensities of illumination of the respective groups of lamps irrespective of the total changes to be effected.

21. In a control system, in combination, an electric circuit, an electrical translating device in said circuit, a rheostat operatively associated with said translating device, said rheostat having an adjustable contactor movable throughout a predetermined range to vary an electrical condition of said translating device, a driving element and means operable automatically for controlling the operation of the latter, means providing a frictional driving connection between said driving element and said contactor, means for rendering said driving connection effective or ineffective, said means comprising an electromagnetically controlled latch, a selector switch and a drum associated with said selector switch, said drum operatively controlling said latch to render said driving connection continuously effective or intermittently effective for predetermined periods, to thereby predetermine the rate of movement of said control element, and means including a synchronous motor for effecting continuous rotation of said drum, said drum having all of the stationary and movable contacts thereof arranged to minimize arcing therebetween.

22. In a control system, in combination, an electric circuit, a rheostat in said circuit, and an "electrical translating device operatively associated with said rheostat and said circuit, said rheostat having an element thereof movable throughout a given range to vary an electrical condition of said circuit, a motor-operated drive, a slip-clutch connection between said drive and said rheostat element, a latch member spring biased into engagement with a part of said element to render said slip-clutch connection ineffective, an electromagnetic relay adapted when energized to retract said latch whereby said slipclutch connection is rendered effective, and means including a selector switch operable at will to provide for energization of said relay either continuously or intermittently for predetermined periods, whereby the rate of opera tion of said element may be definitely preselected.

RICHARD B. HUNTER. 

